Fig. 1.

Methylation patterns in MDS/AML and mechanisms of action of AZA and DAC. 1) In normal human cells, CpG islands in the promoter region of tumor suppressor genes are unmethylated (indicated by green dots), allowing transcription of these genes. 2) Hypermethylation of tumor suppressor genes (indicated as red dots) in the pathogenesis of MDS leads to silencing of tumor suppressor genes and development of a leukemic phenotype. 3) Treatment with AZA nucleosides causes demethylation of the hypermethylated CpG islands in MDS/AML leading to reactivation of tumor suppressor genes and anti-leukemic effects